Determining device, conveying device, image reading device, and image forming apparatus

ABSTRACT

A determining device includes an acquisition processing portion and a determination processing portion. The acquisition processing portion acquires a signal based on an ultrasonic wave emitted toward an object conveyed in a specific direction. The determination processing portion determines whether or not a first time period is equal to or larger than a predetermined first time threshold, wherein the first time period is a time period during which a level of the signal changes from a predetermined first level threshold to a second level threshold that is smaller than the first level threshold.

INCORPORATION BY REFERENCE

This application is based upon and claims the benefit of priority from the corresponding Japanese Patent Application No. 2019-009520 filed on Jan. 23, 2019, the entire contents of which are incorporated herein by reference.

BACKGROUND

The present disclosure relates to a determining device, a conveying device, an image reading device, and an image forming apparatus.

An image reading device or an image forming apparatus may have a function to determine whether or not a double feeding has occurred in a conveyance path. The double feeding is a phenomenon where a plurality of sheet-like objects are conveyed in the conveyance path in a state of overlapping with each other.

In an image forming apparatus of a related technology, a type of the object (for example, envelope or paper) is set based on a user operation. The image forming apparatus includes an ultrasonic sensor that emits an ultrasonic wave toward the object that is conveyed in the conveyance path, and outputs a signal having a level that changes according to an incident wave from the object. Furthermore, in the image forming apparatus, when the envelope is set as the type of the object, and if a change of the signal in lapse of time does not satisfy a first specific condition that has been determined for the envelope, it is determined that the double feeding has occurred, and a conveyance of the plurality of envelopes is stopped. In addition, when the paper is set as the type of the object, and if a change of the signal in lapse of time does not satisfy a second specific condition that is different from the first specific condition, it is determined that the double feeding has occurred, and a conveyance of the plurality of sheets of paper is stopped.

SUMMARY

A determining device according to an aspect of the present disclosure includes an acquisition processing portion and a determination processing portion. The acquisition processing portion acquires a signal based on an ultrasonic wave emitted toward an object conveyed in a specific direction. The determination processing portion determines whether or not a first time period is equal to or larger than a predetermined first time threshold, wherein the first time period is a time period during which a level of the signal changes from a predetermined first level threshold to a second level threshold that is smaller than the first level threshold.

A conveying device according to another aspect of the present disclosure includes a sensor portion and the determining device. The sensor portion emits an ultrasonic wave toward the object, and outputs the signal having a level that changes according to an incident wave from the object.

An image reading device according to a further aspect of the present disclosure includes the determining device or the conveying device.

An image forming apparatus according to a still further aspect of the present disclosure includes the determining device or the conveying device.

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description with reference where appropriate to the accompanying drawings. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing a configuration of an image forming apparatus according to an embodiment of the present disclosure.

FIG. 2A is a schematic diagram showing a first object viewed from a back side, with a cross section of the first object taken along a two-dot chain line III-III and viewed from a width direction of the first object.

FIG. 2B is a schematic diagram showing the first object placed on a first set portion shown in FIG. 1.

FIG. 3 is a schematic diagram showing a second object viewed from a surface side.

FIG. 4A is a diagram showing a change of a signal in lapse of time when one second object is conveyed in a first conveyance path shown in FIG. 1.

FIG. 4B is a diagram showing a change of a signal in lapse of time when two second objects are conveyed in the first conveyance path shown in FIG. 1 without being deviated in a first direction.

FIG. 4C is a diagram showing a change of a signal in lapse of time when two second objects are conveyed in the first conveyance path shown in FIG. 1 in a state of being deviated in the first direction.

FIG. 4D is a diagram showing a change of a signal in lapse of time when one first object is conveyed in the first conveyance path shown in FIG. 1.

FIG. 5 is a diagram showing a block configuration of the image forming apparatus shown in FIG. 1.

FIG. 6A is a flowchart showing a first part of a processing procedure of a control portion shown in FIG. 5.

FIG. 6B is a flowchart showing a second part of a processing procedure of the control portion shown in FIG. 5.

FIG. 7 is a schematic diagram showing a detailed configuration of an image reading device shown in FIG. 1.

DETAILED DESCRIPTION

The following describes an embodiment of the present disclosure with reference to the accompanying drawings for the understanding of the present disclosure. It should be noted that the following embodiment is an example of a specific embodiment of the present disclosure and should not limit the technical scope of the present disclosure.

In FIG. 1, arrows X1, Y1 and Z1 respectively indicate a front-rear direction, a left-right direction, and an up-down direction of an image forming apparatus 100.

The image forming apparatus 100 is, for example, a copier, a printer, a facsimile, or a multifunction peripheral. The multifunction peripheral includes a plurality of functions such as a copy function, a print function, and a facsimile function. The image forming apparatus 100 includes a main body device 200 and an image reading device 300. It is noted that the image forming apparatus 100 may not include the image reading device 300.

The main body device 200 includes a first set portion 22, a first conveyance portion 23, a first sensor portion 24, an image forming portion 25, a first discharge portion 26, a control portion (namely, determining device) 27. In the main body device 200, a conveying device 400 includes at least the first conveyance portion 23, the first sensor portion 24, and the control portion 27.

A first conveyance path CP1 in which objects A1 are conveyed is provided in the main body device 200. The first conveyance path CP1 extends from a first upstream end CP11 to a first downstream end CP12. Specifically, the first upstream end CP11 and the first downstream end CP12 are provided at predetermined positions in the up-down direction on a right side portion 200A and a left side portion 200B of the main body device 200.

The first set portion 22 is a manual feed tray, and extends diagonally upward right from a position slightly below the first upstream end CP11 on the right side portion 200A. The first set portion 22 is configured such that a plurality of types of objects A1 can be placed thereon. The plurality of types of objects A1 include a first object A11 (see FIG. 2A) and a second object A12 (see FIG. 3).

In FIG. 2A, arrows X2, Y2 and Z2 respectively indicate a length direction, a width direction, and a thickness direction of the first object A11. A frame F1 of FIG. 2A shows a cross section of the first object A11 taken along the two-dot chain line III-III parallel to the length direction, and viewed from one side in the width direction.

The first object A11 is, for example, an unused envelope, and includes a body portion B11 and a flap portion B12. The body portion B11 has a shape of an approximate rectangle when viewed in the thickness direction. The body portion B11 further has a shape of a bag where a plurality of sheets overlap in the thickness direction. Specifically, as shown in the frame F1, one side of the body portion B11 in the length direction is opened, and forms an opening B13. In addition, as shown in the frame F1, the other side of the body portion B11 in the length direction is closed, and forms a closed portion B14. The flap portion B12 extends from the other side of the body portion B11, and closes the opening B13 by being folded. As shown in FIG. 2B, the first object A11 is placed on the first set portion 22 such that the closed portion B14 is along the first upstream end CP11.

In FIG. 3, arrows X3, Y3 and Z3 respectively indicate a length direction, a width direction, and a thickness direction of the second object A12. The second object A12 is, for example, an unused sheet of paper or an OHP sheet, and has a constant thickness over the entire region in the length direction and the width direction. It is noted that the image forming apparatus 100 is configured to form images on a plurality of types of second objects A12 that are different from each other in thickness.

Referring to FIG. 1, the first conveyance portion 23 includes a pickup roller and a pair of conveyance rollers, and feeds an object A1 from the first upstream end CP11 into the first conveyance path CP1. Thereafter, the first conveyance portion 23 conveys the object A1 along the first conveyance path CP1 in a first direction D11 at a predetermined velocity V1. The first direction D11 is directed toward the downstream in the first conveyance path CP1, and is a first example of a specific direction of the present disclosure. In addition, the velocity V1 is a first example of a specific velocity of the present disclosure.

The first sensor portion 24 is a first example of a sensor portion of the present disclosure, and is a transmission-type ultrasonic sensor. As shown in FIG. 2B, the first sensor portion 24 includes a sending portion 241 and a receiving portion 242.

The sending portion 241 sends an ultrasonic wave (hereinafter referred to as a measurement wave) toward a detection position DP1, a position in the first conveyance path CP1 that is set to be immediately on the downstream side of the first conveyance portion 23. The amplitude level of the measurement wave is predetermined.

The receiving portion 242 is disposed to face the sending portion 241 across the detection position DP1. The receiving portion 242 outputs, to the control portion 27, a signal ES1 that is generated based on the measurement wave emitted toward an object A1 that is passing the detection position DP1. Specifically, the signal ES1 has a level (namely, a voltage value) that changes according to the ultrasonic wave (hereinafter referred to as an incident wave) that is incident on the receiving portion 242 based on the measurement wave. The level of the signal ES1 is related to a total thickness of the object A1 that is passing the detection position DP1. More specifically, the level of the signal ES1 is related to the type and number of the objects A1.

The type and number of the objects A1 are roughly divided into cases: (1) one second object A12 is passing the detection position DP1 (see FIG. 4A); (2) two or more second objects A12 aligned in the first direction D11 are passing the detection position DP1 (see FIG. 4B); (3) two or more second objects A12 deviated from each other in the first direction D11 are passing the detection position DP1 (see FIG. 4C); and (4) one first object A11 is passing the detection position DP1 (see FIG. 4D).

In the case (1), as shown in FIG. 4A, in a first time section T11 in which the one second object A12 is not passing the detection position DP1, the signal ES1 represents a first level L11. It is noted that the signal ES1 represents the first level L11 in the first time section T11 in which neither the two or more second objects A12 (see FIG. 4B, 4C) nor the one first object A11 (see FIG. 4D) is passing the detection position DP1. In the case (1), in a second time section T12 in which the one second object A12 is passing the detection position DP1, the signal ES1 represents a second level L12 that is smaller than the first level L11.

In the case (2), as shown in FIG. 4B, in a third time section T13, the signal ES1 represents a level that is smaller than the second level L12. It is noted that FIG. 4B shows an example case where the signal ES1 represents a third level L13 in the third time section T13. In the third time section T13, two second objects A12 in a state of overlapping each other are passing the detection position DP1. It is noted that when three or more second objects A12 are passing the detection position DP1, the level of the signal ES1 changes with time in a similar manner to FIG. 4B.

In the case (3), as shown in FIG. 4C, in the third time section T13, the signal ES1 represents a level (for example, the third level L13) that is smaller than the second level L12, and in a fourth time section T14, the signal ES1 represents the second level L12. In the fourth time section T14, only one of two second objects A12 is passing the detection position DP1.

The case (4) is the same as the case (2) in that the body portion B11 of the first object A11 is composed of a plurality of sheets overlapping each other, but the case (4) is different from the case (2) in that the plurality of sheets are connected to each other by the closed portion B14 or the like. As a result, in a fifth time section T15 from the time when the body portion B11 starts passing the detection position DP1 until a specific time period elapses, the level of the signal ES1 reduces with time and finally reaches the third level L13. The reason is as follows.

As indicated by an arrow E1 in a frame F2 of FIG. 4D, when the measurement wave collides with a first region R11 of the body portion B11, a vibration generated by the collision is transmitted from the first region R11 to a second region R12 of the body portion B11 via the closed portion B14 without being largely attenuated. The first region R11 is a region close to the closed portion B14 of a sheet passing on the sending portion 241 side among the plurality of sheets. The second region R12 is a region close to the closed portion B14 of a sheet passing on the receiving portion 242 side among the plurality of sheets. The vibration transmitted to the second region R12 is transmitted to the receiving portion 242 via the air. In addition, since the first object A11 is conveyed in the first direction D11, as the time elapses, the transmission distance from the first region R11 to the closed portion B14 increases. As a result, the vibration transmitted to the second region R12 reduces with time. Accordingly, as shown in FIG. 4D, the level of the signal ES1 reduces with time and reaches the third level L13. It is noted that the length of the fifth time section T15 is determined by the material and thickness of the first object A11, the velocity V1, and a distance from the closed portion B14 in a reverse direction of the first direction D11.

In addition, in the case (4), as shown in FIG. 4D, in a sixth time section T16, the signal ES1 represents the third level L13, and in a seventh time section T17, the signal ES1 represents the second level L12. The sixth time section T16 is a time section that follows the fifth time section T15, in a time section in which the body portion B11 is passing the detection position DP1. In the seventh time section T17, the flap portion B12 of the first object A11 is passing the detection position DP1 (see FIG. 2A).

Referring to FIG. 1, the image forming portion 25 forms an image on an object A1 conveyed in the first conveyance path CP1, at a position on the downstream side of the first sensor portion 24 in the first conveyance path CP1, based on image data transmitted from the control portion 27. The image forming portion 25 discharges the object A1 with the image formed thereon onto the first discharge portion 26 that is, for example, a discharge tray. It is noted that the image forming portion 25 forms the image by an electrophotographic method or an inkjet method.

The control portion 27 serves as a determination device 27. The control portion 27 includes a processor, a program storage portion that is a ROM or the like, and a working area that is a RAM or the like. The processor executes, by using the working area, a program that is preliminarily stored in the program storage portion. This allows the control portion 27 to control the components of the image forming apparatus 100 comprehensively. It is noted that the control portion 27 may be an electronic circuit such as an ASIC (Application Specific Integrated Circuit) or a DSP (Digital Signal Processor). It is noted that when the image forming apparatus 100 includes the image reading device 300, the control portion 27 may be provided in the image reading device 300.

An image forming apparatus according to a related technology detects whether or not a double feeding has occurred, based on a condition that differs among a plurality of types of objects that may be conveyed in a conveyance path. As a result, in a case where a plurality of types of objects are conveyed in sequence in the conveyance path, the related technology cannot detect correctly whether or not a double feeding has occurred, with regard to at least one of the plurality of types of objects. On the other hand, the image forming apparatus 100 is configured to detect, for each of a plurality of types of objects, whether or not a double feeding has occurred, even in a case where a plurality of types of objects are conveyed in sequence in a conveyance path.

As shown in FIG. 5, in the image forming apparatus 100, the control portion 27 includes an acquisition processing portion 27A, a determination processing portion 27B, a time measurement processing portion 27C, a detection processing portion 27D, and a conveyance controlling portion 27E. When the processor executes the program, the control portion 27 functions as the acquisition processing portion 27A, the determination processing portion 27B, the time measurement processing portion 27C, the detection processing portion 27D, and the conveyance controlling portion 27E.

The acquisition processing portion 27A acquires the signal ES1 from the first sensor portion 24.

The determination processing portion 27B determines whether or not a first time period ET1 (see FIG. 6A) is equal to or larger than a first time threshold TT1 (see FIG. 4D), wherein the first time period ET1 is a time period during which the level of the signal ES1 changes from a first level threshold LT1 (see FIG. 4A to FIG. 4D) to a second level threshold LT2.

The first level threshold LT1, the second level threshold LT2, and the first time threshold TT1 are preliminarily determined in the design and development stage of the image forming apparatus 100 through an experiment or a simulation, and are written in the program.

The first level threshold LT1 and the second level threshold LT2 are determined based on the thickness of the object A1 in a second direction D12 that intersects the first direction D11. The second direction D12 is a first example of an intersecting direction of the present disclosure, and specifically, extends in the up-down direction. As shown in FIG. 4B, the first level threshold LT1 has a value that is between the second level L12 and the third level L13, and is close to the second level L12. The second level threshold LT2 is smaller than the first level threshold LT1, and has a value that is between the second level L12 and the third level L13, and is close to the third level L13. More specifically, as shown in FIG. 4A, the first level threshold LT1 is set such that when one second object A12 is passing the detection position DP1, the level of the signal ES1 exceeds the second level L12. Furthermore, as shown in FIG. 4B, the first level threshold LT1 is set such that when the first object A11 or a plurality of second objects A12 are passing the detection position DP1, the level of the signal ES1 is equal to or smaller than the second level L12 and equal to or smaller than the third level L13.

The first time threshold TT1 shown in FIG. 4D is determined based on the velocity V1 and a distance from an end of the object A1 on the first direction D11 side in the reverse direction of the first direction D11. Here, timings at which the level of the signal ES1 becomes the second level L12 and the third level L13, are referred to as a start time t0 and an end time t1 of the fifth time section T15. The first time threshold TT1 is a time period from the start time t0 of the fifth time section T15 to a time t2 that is close to the end time t1 of the fifth time section T15. More specifically, in the distance from the end on the first direction D11 side in the reverse direction, a distance D31 where the level of the signal ES1 changes from larger than the third level L13 to equal to or smaller than the third level L13, is preliminarily determined through the experiment or the simulation. In this case, the first time threshold TT1 is preliminarily determined to be equal to or smaller than a value that is obtained by dividing the distance D31 by the velocity V1.

The time measurement processing portion 27C measures an elapsed time from the time when the determination processing portion 27B determined that the level of the signal ES1 was equal to or smaller than the first level threshold LT1. The elapsed time is used as the first time period ET1 and a second time period ET2 by the determination processing portion 27B.

The determination processing portion 27B is configured to, after it determines that the first time period ET1 is not equal to or larger than the first time threshold TT1 (namely, is smaller than the first time threshold TT1), determine whether or not a double feeding of the object has occurred, based on the level of the signal ES1 acquired by the acquisition processing portion 27A. Specifically, when it determines whether or not a double feeding of the object has occurred, the determination processing portion 27B determines whether or not the second time period ET2 is equal to or larger than a second time threshold TT2, wherein the second time period ET2 is a time period in which the level of the signal ES1 is equal to or smaller than the first level threshold LT1 (see FIG. 6B), and the second time threshold TT2 (see FIG. 4C) is longer than the first time threshold TT1 (see FIG. 4D).

The second time threshold TT2 is preliminarily determined based on the velocity V1 and a length of a specific object A1 in the first direction D11. The specific object A1 is a second object A12 having the smallest length in the first direction D11 among second objects A12 on which images can be formed by the image forming apparatus 100. The second time threshold TT2 is a time period that is obtained by dividing the length of the specific object A1 by the velocity V1.

The detection processing portion 27D detects whether or not a double feeding of the object A1 has occurred, based on the determination result of the determination processing portion 27B. Specifically, when the determination processing portion 27B determines that the first time period ET1 is equal to or larger than the first time threshold TT1, the detection processing portion 27D detects that a double feeding has not occurred. In this case, the conveyance controlling portion 27E further conveys the object A1 toward the downstream in the first direction D11. When the determination processing portion 27B determines that the first time period ET1 is not equal to or larger (is smaller) than the first time threshold TT1, the detection processing portion 27D detects that a double feeding has occurred. In this case, the conveyance controlling portion 27E stops conveying the object A1 in the first direction D11.

Next, a detailed description is given of the process and control of the control portion 27 in the image forming apparatus 100.

First, the user stacks a plurality of objects A1 on the first set portion 22 (see FIG. 1). The plurality of objects A1 include a first object A11 and a second object A12. In addition, the control portion 27 acquires image data that represents an image to be formed. Specifically, the control portion 27 receives the image data from an information processing apparatus (not shown) that is communicably connected with the image forming apparatus 100 via a network. In a case where the image forming apparatus 100 includes the image reading device 300, the control portion 27 may receive the image data from the image reading device 300. Upon receiving the image data, the control portion 27 repeatedly executes the processes shown in FIG. 6A to FIG. 6C as many times as necessary for one object A1, thereby forming the image represented by the image data on as many objects A1 as necessary. It is noted here that since a double feeding may occur in the first conveyance path CP1, the processes shown in FIG. 6A to FIG. 6C include a double feeding detection process.

In step S101 of FIG. 6, the control portion 27 functions as the conveyance controlling portion 27E. The conveyance controlling portion 27E starts conveying an object A1 on the first set portion 22 by controlling the first conveyance portion 23.

Next, in step S102, the control portion 27 functions as the acquisition processing portion 27A, and acquires a signal ES1 from the first sensor portion 24. Next, in step S103, the control portion 27 functions as the determination processing portion 27B. In order to determine whether or not a double feeding has occurred at the current time, the determination processing portion 27B determines whether or not the level of the signal ES1 is equal to or smaller than the first level threshold LT1 (see FIG. 4A or the like). Upon determining that the level is not equal to or smaller (is larger) than the first level threshold LT1, the determination processing portion 27B determines that a double feeding has not occurred at the current time, and moves the process to step S104; and upon determining that the level is equal to or smaller than the first level threshold LT1, the determination processing portion 27B moves the process to step S106.

In step S104, the control portion 27 functions as the detection processing portion 27D and the conveyance controlling portion 27E. The detection processing portion 27D detects that a double feeding has not occurred in the first conveyance path CP1. In this case, the conveyance controlling portion 27E continues the conveyance of the object A1 by controlling the first conveyance portion 23.

Next, in step S105, the conveyance controlling portion 27E determines whether or not it is a stop timing to stop the pickup roller of the first conveyance portion 23. The stop timing is a timing immediately after a rear end of the object A1 in the first direction D11 has passed the pickup roller. Specifically, the conveyance controlling portion 27E determines whether or not it is the stop timing based on an output signal of an optical sensor or the like provided near the first upstream end CP11. Upon determining that it is the stop timing, the conveyance controlling portion 27E stops the pickup roller, ends the processes of FIG. 6A to FIG. 6C, and waits for a next object A1 to be conveyed. In addition, upon determining that it is not the stop timing, the conveyance controlling portion 27E returns the process to step S102.

When one second object A12 is conveyed in the first conveyance path CP1 (see FIG. 4A), a process loop that is composed of steps S102 to S105 executed in the stated order, is repeated. In this case, the image forming portion 25 forms the image on the second object A12 that is being conveyed. Thereafter, the second object A12 with the image formed thereon is discharged onto the first discharge portion 26.

In step S106, the control portion 27 functions as the time measurement processing portion 27C, and starts measuring an elapsed time from the time when the execution of step S106 was started. Next, in step S107, the control portion 27 functions as the acquisition processing portion 27A and acquires a signal ES1 from the first sensor portion 24. Next, in step S108, the control portion 27 functions as the determination processing portion 27B, and determines whether or not a double feeding has occurred in the first conveyance path CP1, by determining whether or not the level of the signal ES1 is equal to or smaller than the second level threshold LT2 (see FIG. 4B to FIG. 4D). Upon determining that the level is equal to or smaller than the second level threshold LT2, the determination processing portion 27B determines that one first object A11 (see FIG. 4D) or a plurality of second objects A12 (see FIG. 4B, FIG. 4C) are conveyed in the first conveyance path CP1, and moves the process to step S109. Upon determining that the level is not equal to or smaller (is larger) than the second level threshold LT2, the determination processing portion 27B determines that not one first object A11 but a plurality of second objects A12 are conveyed in the first conveyance path CP1, and moves the process to step S114 of FIG. 6B.

In a case where the process is returned to step S107, the acquisition processing portion 27A acquires the signal ES1 a plurality of times with a time interval therebetween. Here, the time interval is denoted as ΔT, and ΔT is a time period smaller than the first time threshold TT1. The image forming apparatus 100 is designed such that the acquisition processing portion 27A acquires the signals ES1 with the time interval ΔT.

The control portion 27 functions as the determination processing portion 27B and executes steps S109 and S110 in sequence. In step S109, the determination processing portion 27B acquires an elapsed time as the first time period ET1 from the time measurement processing portion 27C, and in step S110, the determination processing portion 27B determines whether or not the first time period ET1 is equal to or larger than the first time threshold TT1. Based on the result of step S110, the determination processing portion 27B determines whether or not a double feeding has occurred in the first conveyance path CP1. Upon determining that the first time period ET1 is equal to or larger than the first time threshold TT1, the determination processing portion 27B moves the process to step S111. Upon determining that the first time period ET1 is not equal to or larger (is smaller) than the first time threshold TT1, the determination processing portion 27B determines that a plurality of second objects A12 are conveyed in the first conveyance path CP1 (see FIG. 4B, FIG. 4C), and that a double feeding has occurred, and moves the process to step S114 of FIG. 6B.

In step S111, the control portion 27 functions as the time measurement processing portion 27C, and ends the measurement of time, and then moves the process to step S112. In step S112, the control portion 27 functions as the detection processing portion 27D, determines that the object A1 that is being conveyed is one first object A11 (see FIG. 4D), and detects that a double feeding has not occurred in the first conveyance path CP1. Furthermore, in step S112, the control portion 27 functions as the conveyance controlling portion 27E, and conveys the one first object A11 further toward the downstream side in the first direction D11. Step S112 is repeated until the conveyance controlling portion 27E determines in step S113 that it is the stop timing.

According to the processes of FIG. 6A to FIG. 6C, in steps S105 to S110, the detection processing portion 27D detects that one first object A11 is passing the detection position DP1 and that a double feeding has not occurred, when it is detected that the first time period ET1 (see FIG. 6A) is equal to or larger than the first time threshold TT1 (see FIG. 4D), wherein the first time period ET1 is a time period during which the level of the signal ES1 changes from the first level threshold LT1 (see FIG. 4A) to the second level threshold LT2. That is, the control portion 27 can automatically determine that the object A1 that is being conveyed in the first conveyance path CP1 is the first object A11, even if the user does not set the type of the object A1 (namely, the first object A11 or the second object A12). Thereafter, a process loop composed of steps S112 and S113 is repeated. The image forming portion 25 forms the image on the object A1 that is being conveyed. Subsequently, the first object A11 with the image formed thereon is discharged onto the first discharge portion 26.

In steps S114 and S115, the control portion 27 functions as the determination processing portion 27B. In step S114, the determination processing portion 27B acquires an elapsed time as the second time period ET2 from the time measurement processing portion 27C. The determination processing portion 27B determines whether or not the second time period ET2 is equal to or larger than the second time threshold TT2. Upon determining that the second time period ET2 is not equal to or larger (is smaller) than the second time threshold TT2, the determination processing portion 27B moves the process to step S116; and upon determining that the second time period ET2 is equal to or larger than the second time threshold TT2, the determination processing portion 27B moves the process to step S117.

In step S116, the control portion 27 functions as the conveyance controlling portion 27E, and continues to convey the plurality of second objects A12 in the first conveyance path CP1.

In step S117, the control portion 27 functions as the time measurement processing portion 27C, and ends the measurement of time. Subsequently, in step S118, the control portion 27 functions as the detection processing portion 27D, determines that a plurality of second objects A12 are passing the detection position DP1 in the first conveyance path CP1 (see FIG. 4B, FIG. 4C), and detects that a double feeding has occurred. Furthermore, in step S114, the control portion 27 functions as the conveyance controlling portion 27E, and stops conveyance of the plurality of second objects A12 in the first direction D11. Specifically, the conveyance controlling portion 27E controls the first conveyance portion 23 to convey the plurality of second objects A12 in a reverse direction of the first direction D11 in the first conveyance path CP1, and discharge the plurality of second objects A12 from the first upstream end CP11 onto the first set portion 22.

The processes of FIG. 6A to FIG. 6C make it possible to provide the determining device 27, the conveying device 400, and the image forming apparatus 100 that can determine whether or not a double feeding has occurred for each of a plurality of types of objects A1 even when the plurality of types of objects A1 (the first object A11 and the second object A12) are stacked on the first set portion 22, and the plurality of types of objects A1 are conveyed in sequence in the first conveyance path CP1.

It is noted that after it is determined in step S108 that the level of the signal ES1 is not equal to or smaller (is larger) than the second level threshold LT2, and before it is determined in step S115 that the second time period ET2 is equal to or larger than the second time threshold TT2, the control portion 27 may determine whether or not the level of each of the signals ES1 acquired with the time interval ΔT is the first level threshold LT1.

In addition, upon determining in step S110 that the first time period ET1 is not equal to or larger (is smaller) than the first time threshold TT1, the control portion 27 may execute steps S117 and S118 without executing steps S114 to S116.

Referring to FIG. 7, the image reading device 300 is provided above the main body device 200. It is noted that the image reading device 300 may be a scanner or the like that is provided independent of the image forming apparatus 100.

The image reading device 300, including an ADF (Automatic Document Feeder) 310, a cover 320, a contact portion 330, and an image reading portion 340, generates image data by optically reading an image of an object A2 that is conveyed, and outputs the image data to the control portion 27 (see FIG. 1, FIG. 5).

The ADF 310 is a document feeding device, and is integrally provided with the cover 320 on an upper surface of the main body device 200. The ADF 310 includes a second set portion 31, a second conveyance portion 32, a second sensor portion 33, and a second discharge portion 34. In addition, in the image forming apparatus 100, the conveying device 400 is provided in the image reading device 300, and includes at least the second conveyance portion 32, the second sensor portion 33, and the control portion 27 (see FIG. 1, FIG. 5).

In addition, a second conveyance path CP2 in which objects A2 are conveyed is provided in the ADF 310. The second conveyance path CP2 extends from a second upstream end CP21 to a second downstream end CP22. Specifically, the second upstream end CP21 is provided at an upper position close to a center in the left-right direction of the ADF 310. The second downstream end CP22 is provided below the second upstream end CP21 in the ADF 310. In the second conveyance path CP2, its upstream portion extends from the second upstream end CP21 leftward, and its intermediate portion, between its upstream portion and its downstream portion, goes downward while bending. The downstream portion extends diagonally upward right from the intermediate portion to the second downstream end CP22.

The second set portion 31 is a supply tray, and provided at an upper-right portion of the image reading device 300. The second set portion 31 is configured such that a plurality of types of objects A2 can be placed thereon. The plurality of types of objects A2 include a first object A21 and a second object A22. The first object A21 is different from the first object A11 only in that it is a used envelope on which an address or the like has been written. The second object A22 is different from the second object A12 only in that it is a sheet of paper or an OHP sheet on which an image or the like has been recorded. As a result, in the following description, the components common to the first object A21 and the second object A22 are assigned the same reference signs, description thereof is omitted, and FIG. 2A and FIG. 3 are used for the explanation. As shown in FIG. 7, the first object A21 is placed on the second set portion 31 such that the closed portion B14 is along the second upstream end CP21.

The second conveyance portion 32 includes a pickup roller and a pair of conveyance rollers, and feeds an object A2 from the second upstream end CP21 into the second conveyance path CP2. Thereafter, the second conveyance portion 32 conveys the object A2 along the second conveyance path CP2 in a third direction D21 at a predetermined velocity V2. The third direction D21 is directed toward the downstream in the second conveyance path CP2, and is a second example of the specific direction of the present disclosure.

The second sensor portion 33 is a second example of the sensor portion of the present disclosure, and is a transmission-type ultrasonic sensor. The second sensor portion 33 includes a sending portion 331 and a receiving portion 332 that face each other across a predetermined detection position DP2. The detection position DP2 is located immediately on the downstream side of the second conveyance portion 32 in the second conveyance path CP2. The second sensor portion 33 is configured to cause the sending portion 331 to emit a measurement wave having a predetermined amplitude level toward the detection position DP2. The second sensor portion 33 causes the receiving portion 332 to output, to the control portion 27, a signal ES2 that is generated based on the measurement wave. The level of the signal ES2 is related to the type and number of the objects A2 that are passing the detection position DP2 (see FIG. 4A to FIG. 4D).

The second discharge portion 34 is a discharge tray, and is provided on the right side of the second downstream end CP22. Objects A2 discharged from the second downstream end CP22 are stacked on the second discharge portion 34.

The contact portion 330 is a translucent, plate-like member such as a glass plate or a resin plate. The contact portion 330 is provided close to a left end on an upper surface of the main body device 200. The contact portion 330 is attached to the upper surface of the main body device 200 so as to be along a lowest end portion of the second conveyance path CP2. A reading region R1 is preliminarily determined on the contact portion 330. The object A2 conveyed in the second conveyance path CP2 passes over the reading region R1.

The image reading portion 340 is a CIS (Contact Image Sensor). The image reading portion 340 is provided in the main body device 200 at a position close to an upper surface thereof. The image reading portion 340 emits light from below the contact portion 330 toward the reading region R1. The image reading portion 340 generates image data representing an image of the object A2 by photoelectrically converting reflected light from the object A2 that passes the reading region R1, and outputs the image data to the control portion 27.

The acquisition processing portion 27A may acquire the signal ES2 from the second sensor portion 33 instead of the first sensor portion 24. In this case, the determination processing portion 27B and the time measurement processing portion 27C execute the processes shown in FIG. 6A to FIG. 6C based on the signal ES2 instead of the signal ES1. The detection processing portion 27D detects whether or not a double feeding of the object A2 has occurred in the second conveyance path CP2, based on the determination result of the determination processing portion 27B. The conveyance controlling portion 27E controls the conveyance of the object A2 by the second conveyance portion 32, based on the detection result of the detection processing portion 27D.

It is to be understood that the embodiments herein are illustrative and not restrictive, since the scope of the disclosure is defined by the appended claims rather than by the description preceding them, and all changes that fall within metes and bounds of the claims, or equivalence of such metes and bounds thereof are therefore intended to be embraced by the claims. 

1. A determining device comprising: an acquisition processing portion configured to acquire a signal based on an ultrasonic wave emitted toward an object conveyed in a specific direction; and a determination processing portion configured to determine whether or not a first time period is equal to or larger than a predetermined first time threshold, wherein the first time period is a time period during which a level of the signal changes from a predetermined first level threshold to a second level threshold that is smaller than the first level threshold.
 2. The determining device according to claim 1, wherein the first time threshold is determined based on: a velocity at which the object is conveyed in the specific direction; and a distance from an end of the object on the first direction side in a reverse direction of the specific direction.
 3. The determining device according to claim 1, wherein the first level threshold and the second level threshold are determined based on a thickness of the object in an intersecting direction that intersects the specific direction.
 4. The determining device according to claim 1, wherein upon determining that the first time period is not equal to or larger than the first time threshold, the determination processing portion further determines whether or not a second time period is equal to or larger than a second time threshold, wherein the second time period is a time period in which the level of the signal is equal to or smaller than the first level threshold, and the second time threshold is longer than the first time threshold.
 5. The determining device according to claim 4, wherein the second time threshold is determined based on: a velocity at which the object is conveyed in the specific direction; and a length of the object in the specific direction.
 6. A conveying device comprising: a sensor portion configured to emit an ultrasonic wave toward the object, and output the signal having a level that changes according to an incident wave from the object; and the determining device according to claim
 1. 7. The conveying device according to claim 6, further comprising: a detection processing portion configured to detect whether or not a double feeding of the object has occurred, based on a determination result of the determining device.
 8. The conveying device according to claim 7, wherein when the determination processing portion determines that the first time period is equal to or larger than the first time threshold, the detection processing portion detects that a double feeding has not occurred, the conveying device further comprising: a conveyance controlling portion configured to, when the detection processing portion detects that a double feeding has not occurred, further convey the object toward a downstream in the specific direction.
 9. The conveying device according to claim 8, wherein when the determination processing portion determines that the first time period is not equal to or larger than the first time threshold, the detection processing portion detects that a double feeding has occurred, and when the detection processing portion detects that a double feeding has occurred, the conveyance controlling portion stops conveying the object in the specific direction.
 10. An image reading device comprising: the determining device according to claim
 1. 11. An image reading device comprising: the conveying device according to claim
 6. 12. An image forming apparatus comprising: the determining device according to claim
 1. 13. An image forming apparatus comprising: the conveying device according to claim
 6. 